This application relates generally to the field of vehicle chassis design, and more particularly to automotive sub-frames.
A sub-frame is a structural vehicle sub-system that carries certain components, such as the engine, drivetrain, radiator, or suspension. The sub-frame is either bolted or welded to the vehicle. When bolted, the sub-frame is equipped with rubber bushings to dampen and isolate vibration and harshness from the rest of the body during vehicle movement. In a powertrain-supporting sub-frame, forces generated by the engine and transmission can be lowered to a level that does not disturb passengers. The most common type of sub-frame is the “K” brace type, which typically carries the lower control arms and steering rack. Another common sub-frame is the perimeter sub-frame, which carries vehicle components in addition to providing support for the engine.
Existing sub-frame designs, however, suffer from poor crash energy management, are very heavy, and have inefficient load path architecture. Such an architecture results in a constrained design having low load and deceleration levels in the structure, such as the bumper, the crash can, or the front rails, early in a crash event (for example, 10 to 15 msec). Generally, sub-frames stop short from reaching the front of the vehicle, so during a crash, the energy is absorbed by the crash can or the front rails. Thus, the sub-frame is not engaged early in the crash and fails to reach the required load and deceleration levels.
Sub-frames are typically heavy, and their rigid design tends to transfer crash load to the rear end of the sub-frame, which can injure passengers seated within the vehicle. A crash can cause significant damage to a sub-frame and may require sub-frame replacement, which is expensive and often difficult. Further, vehicles often include support for a radiator towards the front, which adds considerably to the weight of the vehicle. Radiator supports can be bulky, and they occupy a large amount of space, reducing crashworthiness of the vehicle.
It would be highly desirable to have a light-weight sub-frame design with improved crash energy managing capabilities, which absorbs significant crash energy at the front of the vehicle and isolates the passengers within the vehicle from the impact of the crash.